Self-healing membranes for polymer electrolyte applications

ABSTRACT

A self-healing composite membrane includes a continuous ionomer phase in which is dispersed a plurality of hollow fibers and/or microcapsules each containing a liquid healing agent that includes a dispersion or solution of a healing ionomer in a liquid vehicle. Electrochemical devices employing the self-healing composite membranes are provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority benefit of U.S. Appin. No. 62/032,084,filed 1 Aug. 2014, the entirety of which application is incorporatedherein by reference for all purposes.

BACKGROUND OF THE INVENTION

Polymer electrolyte membranes are widely used in fuel cells, where theymediate the flow of charged particles during cell operation. However,the limited mechanical durability of such membranes adversely impactsthe life of fuel cells and is a key barrier to fuel cellcommercialization. Over their lifetime, the membranes suffer frommechanical and chemical degradation, leading to defects like pinholesand tears which destroy their functionality. Therefore, improvements inpolymer electrolyte membrane durability would be of significantcommercial value.

SUMMARY OF THE INVENTION

The invention provides a self-healing composite membrane including a iscontinuous ionomer phase in which is dispersed a plurality of hollowfibers and/or microcapsules each containing a liquid healing agent thatincludes a dispersion or solution of a healing ionomer in a liquidvehicle. The invention also provides electrochemical devices employingthe self-healing composite membranes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph of a micropipette containing a liquid healingagent in a composite membrane according to the invention, beforerupture.

FIG. 2 is a photograph of a micropipette in the composite membrane shownin FIG. 1 after rupture.

FIG. 3 is a photograph of a micropipette in the composite membrane shownin FIGS. 1 and 2 after self-healing.

FIG. 4 is a photograph of a hollow polymer fiber containing a liquidhealing agent in a composite membrane according to the invention, beforerupture.

FIG. 5 shows the hollow polymer fiber of FIG. 4 after rupture.

FIG. 6 shows the hollow polymer fiber of FIGS. 4 and 5 after thecomposite membrane has self-healed.

FIG. 7 is an SEM image of hollow urea-formaldehyde microcapsulessuitable for containing a liquid healing agent according to theinvention.

FIG. 8 is an SEM image of a urea-formaldehyde (UF) microcapsule cut by afocused ion beam (FIB), revealing its hollow structure.

FIG. 9 shows photographs of a cluster of uncrushed microcapsules (toppane) and crushed microcapsules (bottom pane) containing a dyed NAFION®solution.

FIG. 10 shows fuel cell performance of a NAFION® membrane, a 6 wt %UF/NAFION® membrane, and a 10 wt % NAFION® membrane, all at 70° C. and100% relative humidity.

FIG. 11 shows results of accelerated durability testing over 220 hoursof a 6 wt % UF/NAFION® membrane at 90° C., using an OCV hold with arelative humidity cycling protocol.

FIG. 12 is a schematic representation of a hydrogen fuel cell using aself-healing composite membrane as the electrolyte/membrane layeraccording to the invention.

FIG. 13 is a schematic representation of a water electrolyzer using aself-healing composite membrane as the electrolyte/membrane layeraccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a novel self-healing composite membrane thatincludes a continuous ionomer phase that forms the membrane matrix, inwhich is dispersed a plurality of carrier vessels containing a liquidhealing comprising a dispersion or solution, in a suitable liquidvehicle, of a healing ionomer having the same or similar composition asthe continuous ionomer phase of the membrane. The carrier vessels are inthe form of hollow fibers and/or microcapsules. When the membrane isstressed during operation to the point that pinholes or cracks initiate,the carrier vessels in the immediate neighborhood of the defect ruptureand release the contained polymer dispersion/solution, providing in situhealing of the pinholes and cracks.

Continuous Ionomer Phase

Any ionomer that transports cations or anions is suitable for formingthe continuous ionomer phase according to the invention. Non-limitingexamples include fluorinated sulfonic acid co-polymers oftetrafluoroethylene and any fluorinated polymer containing an acidic orbasic group, preferably a sulfonic acid group for cation-transportingionomers; or fluorinated hydrocarbon co-polymers of aromatic or linearpolymers and a fluorinated polymer containing an acidic or basic group,preferably sulfonic acid for cation ionomers; or hydrocarbon polymers ofaromatic or linear polymers with an acidic or basic group. Oneparticularly desirable cation-transporting ionomer for use according tothe invention comes from the class of perfluorosulfonic acid (PFSA)polymers commonly known by the tradename NAFION®. These and otherionomers bearing acidic substituents may be used in proton exchangemembrane (PEM) fuel cells, electrolyzers, and other applications.Anion-transporting ionomers include quaternary ammonium or quaternaryphosphonium substituents, and these may be used in hydroxide exchangemembrane (HEM) fuel cells, electrolyzers, and other applications.Suitable dispersible alkaline ionomers for making anion-transportingmembranes are available from Tokuyama Co, Japan under the names A3 ver.2and AS-4.

Examples of commercial alkaline anion exchange membranes are sold byTokuyama Co, Japan under the names AHA A010, A201. Other examplesinclude commercial alkaline anion exchange membranes such as Morgane ADP(Solvay S.A.), Tosflex® SF-17 (Tosoh) and 2259-60 (Pall RAI). Any ofthese can be dissolved in suitable solvents, and the resulting solutionscombined with carrier vessels loaded with liquid healing agent and usedto cast composite membranes according to the invention.

The continuous ionomer phase may consist of the ionomer. Or, it mayadditionally contain any of a number of additives known in the art forpreparing membranes. Non-limiting examples include CeO₂ and MnO₂nanoparticles, as well as hydrophilic inorganic particles (e.g., SiO₂and TiO₂) and carbon nanotubes or porous PTFE reinforcing structures.Heteropolyacids may also be included, for example to improve protonconductivity.

Carrier Vessels

Carrier vessels may for example be any one of the following, eithersingly or in combination: hollow microfibers, microcapsules, glasstubes, micropipettes, or any other structure that is substantiallyimpermeable to the contents of the vessels and to any solvents used tocast the continuous ionomer phase. Generally, the contents arecompletely encapsulated such that the vessels must be ruptured for anyoutflow of liquid healing agent to occur.

It is desirable that it be possible to rupture the carrier vessels uponexposure to one or more stresses. The rupture may result from mechanicalstresses and be due to inherent material properties, for example beingbrittle, or because of design, for example having very thin walls. Or,the stresses may be thermal. For example, the carrier vessels may bedesigned to rupture when the temperature exceeds normal fuel celloperating temperatures, which are typically 60-80° C., or when thetemperature falls low enough to damage the fuel cell, typically about−40° C.

The vessels, whether hollow fibers or microcapsules, can be made from arange of materials, including but not limited to polymers, for examplepolytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), orfluorinated ethylene propylene (FEP); ceramics, for example glass oralumina; and metals, for example platinum, iron or silver.

If the carrier vessels are hollow fibers, they may be randomly orientedin the membrane or they may be oriented along one or more defined axes.For example, they may all be disposed parallel to a single axis, or somemay be disposed parallel to one axis and the rest disposed to adifferent an axis, e.g., one orthogonal to the first. Such placementscan be effected manually, if needed, although more automated methods arepreferred.

One typical material for forming microcapsules is a urea-formaldehydecondensate. Or, microcapsules having a crosslinked chitosan shell can beprepared by the method described by Liu etc. in Soft Matter, 2011, 7,4821. Polymethylmethacrylate (PMMA) and polyamide microcapsules can bemade using interfacial polycondensation or polymerization, for exampleas described in Defence Science Journal, Vol. 59, No. 1, January 2009,pp. 82-95. Melamine-formaldehyde microcapsules can be made as describedin International Journal of Pharmaceutics, Volume 242, Issues 1-2, 21Aug. 2002, Pages 307-311. The shell material can also bepolytetrafluoroethylene (PTFE), which may be prepared by polymerizingliquid tetrafluoroethylene as described in U.S. Pat. 5,405,923, butdoing so in the presence of dispersed droplets of liquid healing agentat a stirring speed selected to provide capsules of the desired size.Shells of polyether ether ketone (PEEK) can be obtained by step-growthpolymerization by the dialkylation of bisphenolate salts as generallydescribed in Journal of Polymer Science Part A: Polymer Chemistry,Volume 33, Issue 2, pages 331-344, 30 Jan. 1995. The reaction would beperformed in the presence of dispersed droplets of liquid healing agentat a stirring speed selected to provide capsules of the desired size.

Poly(ether sulfone)s and sulfonated poly(ether sulfone)s, may besynthesized by direct polymerization of bisphenols and aromaticdihalides in N-methyl-2-pyrrolidone (NMP) at 130° C., as described inPolym. Adv. Technol. 2006; 17: 591-597. The reaction would be performedin the presence of dispersed droplets of liquid healing agent at astirring speed selected to provide capsules of the desired size.

The vessels have at least one external dimension less than 2 mm, or lessthan 1 mm, 500 μm, 250 μm, 150 μm, 100 μm, 50 μm, 30 μm, 20 μm, 10 μm,or 5 μm. Typically, this external dimension will be at least 1 μm. Inthe case of hollow fibers, these numbers relate to the outside diameter.In the case of oval vessels, this relates to the largest outsidecircular diameter, or the outside diameter in the case of sphericalvessels. The appropriate size can be selected to match the desiredmembrane thickness for the particular end-use. Larger carrier vesselsmay be used for thicker membranes, and smaller ones are preferred inapplications where thinner membranes are desirable. Typically, thevessels have at least one external dimension that is less than 80% ofthe membrane thickness, or less than 40% or 20%. For example, when theapplication demands a thin membrane for performance reasons, for examplea membrane thickness of 25 μm, then the lowest outer dimension of thecarrier vessel should be less than 20 μm, and preferably less than 10μm, and most preferably less than 5 μm.

The filled vessels typically constitute at least 1% by weight of thecomposite membrane, or at least 2%, 3%, 4%, 5% or 6%. They typicallyconstitute at most 20%, or at most 15%, 14%, 13%, 12%, 11% or 10% of thecomposite membrane.

Liquid Healing Agent

The liquid healing agent includes a healing ionomer, which is typicallythe same or similar ionomer as that which forms the continuous ionomerphase of the composite membrane. If the ionomer of the continuous phaseis a cation-transporting ionomer, the healing ionomer should transportthe same type of cations. Similarly, if the ionomer of the continuousphase is an anion-transporting ionomer, the healing ionomer shouldtransport the same type of anions.

A solvent or other liquid vehicle for the healing ionomer is alsoincluded in the liquid healing agent. Typically, although notnecessarily, the solvent or other liquid vehicle is volatile enoughthat, once the liquid healing agent has been released from a carriervessel, the solvent or vehicle can evaporate from the compositemembrane. This may occur at room temperature, or at fuel cell operatingtemperature (typically 60° C. to 80° C.). Or, it may be extracted fromthe liquid healing agent by contact with water during operation of thecell. In any case, loss of the solvent or liquid vehicle causes thepolymer to solidify and thereby heal nearby defects. Since most fuelcell membrane ionomers are soluble in common solvents (e.g., ethanol,ethylene glycol and tributyl phosphate), liquid vehicles including these(optionally with some water present) may be suitable for preparingdispersions or solutions of the healing ionomer. A crosslinker capableof crosslinking the ionomer in the continuous ionomer phase may also beincluded in it, optionally with a catalyst for the crosslinkingreaction. The crosslinker may also be capable of crosslinking thehealing ionomer upon its release from the carrier vessels, although thisis not required. One exemplary class of crosslinking agents ispolybenzimidazoles, as described in Journal of Power Sources Volume 163,Issue 1, 7 Dec. 2006, Pages 9-17.

The healing ionomer typically constitutes at least 5 wt %, or at least10, 20 or 30 wt %, of the liquid healing agent. It typically constitutesat most 90 wt %, or at most 80, 70 or 60 wt %, of the liquid healingagent. The balance is the solvent or other liquid vehicle, optionallycontaining a catalyst and/or crosslinker. If a catalyst and/orcrosslinker are present, they together typically constitute from 1 wt %to 5 wt % of the liquid healing agent.

The liquid healing agent may be deposited within the carrier vesselusing standard approaches known in the art. For example, for hollowfibers, the liquid healing agent can be drawn in by vacuum. Filledmicrocapsules can be produced in situ by appropriately controlling thechemistry of the microcapsule during its formation.

Making the Membranes

Ionomer membranes according to the invention can be prepared usingvarious processes known in the art, including but not limited tosolution casting or extrusion. The carrier vessel is incorporated withthe ionomer prior to membrane preparation using standard mixingapproaches known in the art, including but not limited to stirring orother blending approaches for particulate-like materials. Fibrous,mat-like, or microcapsule carrier vessels can typically be used directlyand the membranes formed using standard pre-preg or solution methods.Care must be taken during membrane preparation not to damage the carriervessel, which would potentially allow the liquid healing agent containedwithin it to prematurely leak out during preparation. The ionomermembrane is then formed in the desired thickness. Solution casting isparticularly preferable because it does not unduly stress the carriervessels, and can be used to easily prepare a range of membranethicknesses, from a few pm up to 2 mm or more. The particular membranepreparation parameters used depend on the ionomer, and are well known inthe art. For example, for PFSA-based ionomers using alcohol solvents,membranes can be solution cast between room temperature and 80° C., andsubsequently dried in air from room temperature to 150° C.

Suitable casting solvents are known to the skilled person, andnon-limiting examples include dimethylacetamide, dimethylformamide,N-Methyl-2-pyrrolidone and dimethyl sulfoxide. Solutions of NAFION®polymer in any of these solvents can be prepared by evaporating thewater/alcohol solvent from a commercial NAFION® solution andre-dissolving the polymer in the selected solvent.

Membranes according to the invention typically have a thickness of atleast 1 μm, or at least 2, 5 or 10 μm. The thickness is typically atmost 5000 μm, or at most 4000, 3000, 2000, 1000, 500, 250, 100 or 50 μm.Typically, the length and width of the membrane are each independentlyat least 10 times the thickness, or at least 20, 50 or 100 times thethickness. These same values apply to the diameter, if the membrane iscircular.

Devices Employing the Membranes

Ionomer membranes according to the invention can be used in a variety ofapplications where durable, ionomer membranes are required. Themembranes require no special handling after preparation. During use,should the ionomer membrane be stressed due to mechanical stresses,thermal stresses, chemical stresses, or suffer other physical damage,the carrier vessel within the ionomer membrane will rupture and releasethe liquid healing agent contained within it, thereby mitigating theeffects from the outside stresses. For example, if a crack or hole isformed in the ionomer membrane, the liquid healing agent contained inthe carrier vessel will be released and can fill the hole or blunt thecrack tip, thereby increasing the durability of the ionomer membrane.Typical uses of the inventive membrane include, but are not limited tofuel cells, batteries, sensors, or any other electrochemical applicationwhere durable membranes capable of ion transport are required. These mayinclude, but are not limited to, redox flow batteries, zinc-airbatteries and other metal-air batteries, solar hydrogen devices,desalination devices, and electrodialysis devices. The skilled personwill be aware of how to incorporate the membranes in these devices.

Fuel Cells and Electrolyzers Using Self-Healing Membranes

In some embodiments of the invention, self-healing membranes may be usedin hydrogen fuel cells or water electrolyzers. Numerous configurationsand methods of making hydrogen fuel cells and water electrolyzers andare known to the skilled person, and self-healing membranes according tothe invention may be used as electrolytes/membranes in any of these.Schematic representations of a fuel cell and an electrolyzer are shownin FIGS. 12 and 13, respectively. In these drawings, HER refers tohydrogen evolution reaction, OER refers to oxygen evolution reaction,HOR refers to hydrogen oxidation reaction, and ORR refers to oxygenreduction reaction. Suitable examples of catalysts for each of thesereactions are known to the skilled person.

Self-healing membranes may also be used in fuel cells using fuels otherthan hydrogen. They may also be used in membranes for otherelectrochemical devices and processes including, but not limited to,batteries, for example redox flow batteries, zinc-air batteries andother metal-air batteries, solar hydrogen devices, desalination devices,sensors, electrodialysis devices, or any other electrochemicalapplication where durable membranes capable of ion transport arerequired. The skilled person will be aware of how to incorporate themembranes in these devices.

EXAMPLES

Three sets of experiments to demonstrate the self-healing concept aredescribed below. The first set pertains to the use of a carrier vesselconsisting of a mm-scale micropipette. The second corresponds to acarrier vessel consisting of a 100 μm-scale FEP hollow polymer fiber.The third corresponds to a 5 μm urea-formaldehyde microcapsule. Allreferences to NAFION® polymer in the Examples refer to perfluorosulfonicacid polymer having an equivalent weight of 1000EW. This polymer is soldas a 5 wt % solution in alcohol/water by DuPont under the name NAFION®D520 1000EW.

Example 1 Carrier Vessels Formed from Micropipettes

A composite membrane was prepared, incorporating a carrier vesselconsisting of a micropipette (IDEX Health & Science LLC, 1.5 mm OD and 1mm ID, PEEK) filled with NAFION® D520 1000EW. The micropipette wasfilled using a mild vacuum applied by a rubber bulb. A few drops of adark dye (STEEL BLUE® Layout Fluid, Dykem) were added to the solutionprior to filling the micropipette. The dye was included to allowhigh-contrast photographs to be taken later. The ends of themicropipette were then sealed with epoxy (3M, DP460NS) and allowed toharden. The resulting micropipette was laid flat on a surface andNAFION® D520 1000EW was cast over it and allowed to dry slowly over 24hours. The resultant membrane was a pore-free solid film about 2 mmthick with an embedded micropipette filled with NAFION® solution.

To simulate defects that might occur during fuel cell operation, themembrane is was subjected to mechanical damage by manually rupturing themicropipette by drilling into it with 0.3 mm drill. FIGS. 1 and 2 showthe micropipette before and after drilling, respectively. In FIG. 2, thehole is rendered visible by having the same light color as the membranesurrounding the micropipette. Fuel cell operation (60° C.-150 C.) wasthen simulated by applying heat to one end of the composite membrane,causing the solution to emerge from the micropipette. The result wasthat the hole was filled with ionomer solution, as observed by the holebecoming dark like the rest of the solution in the micropipette (FIG.3). After subsequent drying, the hole was completely filled and sealedwith ionomer, thus healing the defect.

Example 2 Carrier Vessels Formed from 100 μm FEP Hollow Polymer Fibers

A composite membrane was prepared, incorporating hollow polymer fibers(Paradigm Optics, 125 μm OD and 100 μm ID, FEP) filled with NAFION® D5201000EW. The fibers were filled by capillary action. A few drops of redliquid dye (Rit) were added to the solution prior to filling the fibers,to allow high-contrast photographs to be taken. The ends of the fiberswere then melted and sealed over an open flame. The resulting fiberswere laid flat on a surface and NAFION® D520 1000EW was cast over it andallowed to dry slowly over 24 hours. The resultant membrane formed apore-free solid film that was about 135 μm thick and incorporated thefibers filled with NAFION® solution.

To simulate defects that might occur during operation, the membrane wassubjected to mechanical damage by cutting it with a blade such that oneor more of the filled fibers were cut. FIGS. 4 and 5 show one of thefibers before and after cutting. In FIG. 5, the long black vertical lineis the crack in the membrane resulting from the cutting. Fuel celloperation (60° C.-150° C) was then simulated by applying heat to thecomposite membrane, causing the healing liquid to emerge from the fibersand fill the crack. After subsequent drying, only traces of the crackremained, seen as the thin black vertical line at the very top of FIG.6. Thus, the solution effectively healed the defect.

Example 3 Composite Membrane Using 5 μm Urea-Formaldehyde Microcapsules

Microcapsules containing a liquid healing agent were prepared asfollows. A 300 mL beaker containing 100 mL of water and equipped with athermocouple and a stirring blade was set on hot plate. To this wasadded 1.25 g urea (Aldrich), 0.125 g ammonium chloride and 0.125 gresorcinol. The solution was stirred by blade at 1000 rpm for 10 minutesto provide a homogenous solution, and then 20 mL of a 5 wt % solution ofNAFION® polymer in tributyl phosphate was added with continued stirringto form an oil-in-water emulsion. The stirring speed was set at 1000 rpmto obtain the desired microcapsule size. The pH was adjusted to 3.5 with20% NaOH, followed by addition of 3.165 g of 37% formaldehyde (Aldrich).After 30 minutes of stirring, the beaker was covered with plastic film.Then the mixture was brought to 50° C. and then maintained at thattemperature for 4 hours. The resulting microcapsules were then separatedby filtering and dried.

FIG. 7 shows SEM images of the resulting UF microcapsules, which rangedin diameter from 2 to 10 μm with an average size of 5.85 μm. FIG. 8reveals the hollow structure of a typical microcapsule, exposed bycutting it with a focused ion beam.

To verify that hollow microcapsules prepared by this method were indeedfilled with NAFION® solution, a batch of microparticles was prepared inwhich the solution of NAFION® polymer in tributyl phosphate was dyeddark blue with STEEL BLUE® Layout Fluid (Dykem). The resulting particleswere isolated and dried for at least a week under ambient conditions. Asmall portion of the dried microcapsules was then placed between twoclean, dry glass slides. The upper pane of FIG. 9 shows a cluster of themicrocapsules prior to applying finger pressure, which crushed themicrocapsules and released the dyed liquid healing agent, as seen by theincreased size of the dark spot in the lower pane of FIG. 9. Thisconfirms that the microcapsules had been successfully filled with theNAFION® solution, which was released by mechanical damage.

To form a composite membrane according to the invention, microcapsulesprepared as described above (without the dye) were added at variousloadings (0 wt %, 6 wt % and 10 wt %) to 5 wt % solutions of NAFION®polymer in dimethylacetamide, and each mixture was poured into a castingframe to cast a membrane and allowed to dry slowly at 60° C. over 24hours. The resulting membranes were pore-free solid films about 50 μmthick, with the 0 wt % membrane serving as a control.

The fuel cell performances of the 0 wt %, 6 wt % and 10 wt %microcapsule membranes were tested in a 10 cm² cell at 70° C. and100%RH, with H₂ and O₂ flow rates of 200 and 400 mL/min, respectively.As shown in FIG. 10, fuel cell performance of the 6 wt % microcapsulemembrane compared well with that of the baseline 0 wt % membrane, butperformance of the 10 wt % membrane was significantly worse than that ofthe baseline membrane. This suggests that, in this particularembodiment, the 10 wt % microcapsule loading was too high to be optimal.

Accelerated durability testing of the 6 wt % microcapsule membrane wasconducted at 90° C., using an OCV hold with RH cycling protocol. Each RHcycle consisted of a 30 second wet step followed by a 45 second drystep. This protocol was designed to simultaneously generate bothchemical degradation (OCV hold) and mechanical degradation (RH cycling).As shown in FIG. 11, the 6 wt % microcapsule membrane showed stable OCVover the entire 220 hours (10,000 cycles) test.

Although the invention is illustrated and described herein withreference to is specific embodiments, the invention is not intended tobe limited to the details shown. Rather, various modifications may bemade in the details within the scope and range of equivalents of theclaims without departing from the invention.

1. A self-healing composite membrane comprising a continuous ionomerphase in which is dispersed a plurality of hollow fibers and/ormicrocapsules each containing a liquid healing agent that comprises adispersion or solution of a healing ionomer in a liquid vehicle.
 2. Thecomposite membrane according to claim 1, wherein the composite membranecomprises said plurality of microcapsules.
 3. The composite membraneaccording to claim 2, wherein the microcapsules are urea-formaldehydemicrocapsules.
 4. The composite membrane according to claim 1, whereinthe composite membrane comprises said plurality of hollow fibers.
 5. Thecomposite membrane according to claim 1, wherein the plurality of hollowfibers are oriented randomly.
 6. The composite membrane according toclaim 1, wherein some of the plurality of hollow fibers are orientedalong a first axis, and the rest are oriented along an axis orthogonalto the first.
 7. The composite membrane according to claim 1, whereinthe ionomer of the continuous ionomer phase is a cation-transportingionomer.
 8. The composite membrane according to claim 7, wherein thecation-transporting ionomer is a perfluorosulfonic acid polymer.
 9. Thecomposite membrane according to claim 1, wherein the ionomer of thecontinuous ionomer phase is an anion-transporting ionomer.
 10. Thecomposite membrane according to claim 9, wherein the anion-transportingionomer comprises quaternary ammonium groups.
 11. The composite membraneaccording to claim 9, wherein the anion-transporting ionomer comprisesquaternary phosphonium groups.
 12. The composite membrane according toclaim 1, wherein the healing ionomer is the same as the ionomer of thecontinuous ionomer phase.
 13. An electrochemical device employing thecomposite membrane according to any prcccding claim
 1. 14. Theelectrochemical device according to claim 13, wherein theelectrochemical device is a fuel cell.
 15. The electrochemical deviceaccording to claim 13, wherein the electrochemical device is anelectrolyzer.
 16. The electrochemical device according to claim 13,wherein the electrochemical device is a battery.
 17. The electrochemicaldevice according to claim 13, wherein the electrochemical device is asolar hydrogen device.
 18. The electrochemical device according to claim13, wherein the electrochemical device is a desalination device.
 19. Theelectrochemical device according to claim 13, wherein theelectrochemical device is an electrodialysis device.